Apparatus for moisture removal



Aug 4, 1959 1 H. CONNELL ET AL 2,898,431

APPARATUS -FoR MOISTURE REMOVAL 'Filed Feb. 1e, 1955 2 Sheets-Sheet 1 hfrzmrg- Lou/eI] A Moe 2 Lawrerce H Connell 5 f wf @Wi fd'a Aug. 4, 1959 1 H. CONNELL ETAL 2,898,431

APPARATUS FOR MOISTURE REMOVAL Filed Feb. 16, 1955 2 sheets-sheet 2 //o3 /mg 'zg.

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` f au ence HConne nited States Patent APPARATUS FOR MOISTURE REMOVAL Lawrence H. Connell, Haines City, Fla., and Lowell A.

Moe, Eau Claire, Wis., assignors, by mesne assignments, to F. H. Peavey & Company, Minneapolis, Minn., a corporation of Minnesota Application February 16, 1955, Serial No. 488,687

2 Claims. (Cl. 219-10.77)

between which the material to be treated is disposed.

Another object is to provide an improved arrangement whereby electrodes may 'be moved conjointly toward and away from each other.

According to this invention, a high frequency source is provided having a class-C operated output stage coupled to the electrodes and a relay is provided responsive to current drawn by said stage from power supply means used to apply voltage thereto, the relay means including contact means operated in one direction when the current is less than a certain value and in the reverse direction when the current is greater than a certain value. Means are provided controlled by the contact means to energize electro-mechanical means coupled to adjustment means controlling the spacing of the electrodes, in a manner such that the spacing of the electrodes is decreased when the current is below a certain value and is increased when the current is above a certain value. With this arrangement, the high frequency power applied to the material may be maintained substantially constant within limits.

A further feature of the invention is in the provision of a pair of racks connected to and disposed in transverse relation to the electrodes and in spaced parallel relation to each other with a gear positioned between and having opposite sides meshed with the racks, to control movement of the electrodes oonjointly toward or away from a region in which the material is disposed. This facilitates the control of applicationof the high frequency power, since both electrodes may be maintained in substantially the same relationship to the material.

This invention contemplates other objects, features and advantages which will become more fully apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate preferred embodiments and in which:

Figure 1 isa top plan view of a portion of a machine constructed in accordance with the principles of this invention, and particularly adapted for the Itreatment of wood or similar vegetable fibrous materials;

Figure 2 is a schematic electrical circuit diagram of an arrangement for supplying high frequency power to and controlling the operation of the machine of Figure 1;

Figure 3 is an isometric view illustrating diagrammatically a machine constructed in accordance with the principles of this invention and arranged for treating lignite or similar materials;

Figure 4 is an isometric view illustrating diagrammatically a machine for treating paper or the like materials; and

Figure 5 is a sectional View taken substantially along line V-V of Figure 4.

ICC

Reference numeral 10 designates one preferred embodiment of moisture-removal machine constructed in accordance with the principles of this invention, the machine 10 being particularly arranged for the treatment of wood or similar materials. The machine 10, shown in plan in Figure l, may comprise a table 11 having a horizontal surface for receiving thereagainst a board, plank or similar wood article 'to be treated, the position of a plank 12 being indicated by broken lines in Figure l. Means, not shown, may be provided for moving the plank 12 longitudinally, and the lateral position of the plank 12 may be fixed by means of a first pair of rollers 13 and 14 and a second pair of rollers 15 and 16 for engaging oppositely facing parallel surfaces of the plank 12.

Intermediate the first pair of rollers 13 and 14 and the second pair of rollers 15 and 16, a pair of plates 17 and 18 may be arranged in spaced facing relation on the opposite sides of the plank 12, the surfaces of the plates 17 and 18 being thus in facing relation to the oppositely facing surfaces lof the plank 12. These plates 17 and 18 form electrodes to which a high frequency voltage may be applied for treatment of the plank 12 to remove moisture therefrom. The means for application of such a voltage to the plates 17 and 18 will be described in detail hereinafter.

As indicated in the foregoing preliminary discussion, it is desirable that the spacing between electrodes and the surfaces of material under test be controlled so as to prevent excessive high frequency current to the material. This is particularly true in the case of wood or similar materials.

For so controlling movement of the plates 17 and 1S, the plate 17 may be supported from a plate 19 and the plate 18 may be supported from a plate 20 with insulating sheets 21 and 22 interposed between the plates 17 and 19 and the plates 18 and 20, respectively. The plates 19 and 20 are respectively carried by bars 23 and 24 journalled for longitudinal, non-rotative movement in ways 25 and 26 secured to the table 11. The bars 23 and 24 may carry, through the plates 19 and 20, racks 27 and 28, respectively, disposed below the level of the horizontal upper surface of the table 11. It may be noted that the table 11 may have a generally rectangular opening about the electrode plates 17 and 18 and associated structure, as is illustrated.

The racks 27 and 28 may have facing toothed edges 29 and 30, respectively, and a pinion 31 rotatable on a vertical axis may have teeth meshed with the teeth of the toothed edges 29 and 30 of the racks 27 and 28. With this arrangement, by rotating the pinion 31 in one direction, for example, clockwise as viewed in Figure 1, the plates 27 and 28 will be moved toward each other while by moving the pinion 31 in the opposite direction, for example, counter-clockwise as viewed in Figure 1, the plates 17 and 18 will be moved away from each other.

To control movement of the pinion 31, it may be secured to a worm wheel 32 having peripheral teeth meshed with a worm 33 rotatable on a horizontal axis. The worm 33 may be carried by a shaft 34 journalled for rotation in a suitable support 35, the shaft 34 being coupled to the drive shaft of an electric motor 36 disposed below the table 11. The motor 36 is reversible and by appropriate energization of the motor 36, the movement 0f the electrode plates 17 and 18 may be controlled.

To prevent lost-motion and achieve smooth control of the movement of the plates 17 and 18 in opposite directions, a pair of coiled compression springs 37 and 38 mayy be disposed on the bars 23 and 24, respectively, between the way 25 and plate 19 and Way 26 and plate 20.

For applying high frequency voltage to the electrode plates 17 and 18, :they may be respectively connected'.

through flexible leads 39 and 4t) to suitable terminals 41 and 42, which may be affixed to the ways 25 and 26, and the terminals 41 and 42 may be respectively connected through wires 43 and 44 to a suitable source of high frequency voltage.

A preferred source of high frequency voltage is shown schematically in Figure 2 and is designated by reference numeral 45. The source 45 may comprise a push-pull oscillator including a pair of space discharge devices 46 and 47 having cathodes 4S and 49, grids 5t) and 51 and plates 52 and 53. The cathodes 4S and may be connected together and to a terminal 54 arranged to be connected to the negative side of a power supply (to be described) and the plates 52 and 53 may be connected to opposite ends of a coil 55 having a center tap connected to a terminal 56 arranged to be connected to the positive side of a power supply. The coil 55 is inductively coupled to a coil 57 connected to terminals 58 and 59 which may be respectively connected to the wires 43 and 44 so as to be connected to the electrode plates 17 and 18. A suitable variable capacitor 60 may be connected across the output coil 57 between the terminals 5S and 59, and the adjustment of this circuit will be described more in detail hereinafter. The oscillator defined by the discharge devices 46 and 47 rnay preferably be a tuned plate-tuned grid oscillator and the grids t) and 51 of the devices 46 and 47 may be connected to opposite ends of a coil 61 and to a variable capacitor 62. The coil 61 may have a center tap connected through a grid-leak resistor 63 and capacitor 64 to the cathodes 48, 49, hence to the terminal 54 arranged to be connected to the negative side of a power supply. The resistor 63 and capacitor 64 may provide class C bias for the oscillator, i.e. 11/2 to 4 times the cutoff bias for the devices 46-47, for a reason which will appear more clearly hereinafter.

It will be appreciated that in `order to obtain maximum power and highest etliciency from the high frequency supply 45, the tuning of the grid tank circuit defined by coil 61 and capacitor 62 must be properly related to the tuning of the plate circuit. The tuning of the plate circuit is affected not only by the inductances and mutual couplings of the coils 55 and 57 and the capacitance of the capacitor 60, but is also affected by the capacitance between the plates 17 and 18 which may be considerable, wood having dielectric properties, as will be appreciated by those skilled in the art. At the desired frequency of operation of the machine, therefore, the effective internal impedance of the source 45, as viewed from the terminals 58 and 59 may be inductive in nature so that when the material to be treated, such as the plank 12, is disposed between the plates 17 and 18, the capacitance defined by the plates 17 and 1S cooperating with such material will tune the circuit to resonance at the desired frequency.

The frequency of operation of the machine is not critical and should be chosen so as to meet F.C.C. requirements. It may, for example, be in the order of 25 megacycles.

It will be appreciated that resonance between the grid and plate circuits may be achieved by tuning the capacitor 62 in the grid circuit. However, with variations in the composition, thickness and width of the material disposed between the plates 17 and 18, the frequency of operation of the source may be thrown out of a desired range of operation. To avoid this, the tuning of the grid circuit may be substantially constant, and variations in the characteristics of the material under test may be compensated for by tuning the capacitor 60 connected between the output terminals 5S and 59. It may be noted that the source 45 may have a comparatively large power output in the order of 500 to 1000 watts, and even greater under some circumstances, and it will be appreciated that it may be very difficult to avoid a certain amount of radiation from this circuit. It is desirable that any such radiation should not interfere with surrounding television receivers, FM receivers, amateur or commercial reception, and it may therefore be desirable that the source 45 be operated at a selected frequency where such interference will not occur. The provision of the capacitor 60 may therefore become particularly desirable.

To supply power for the source 45, a power supply generally designated by reference numeral 65 may be provided. The supply 65 may comprise a negative output terminal 66 connected to the terminal 54 of the high frequency source 45 and a positive terminal 67 connected to the terminal 56. The negative terminal 66 may be connected to the center tap of a high voltage secondary winding 68 of a transformer 69, the ends of the winding 68 being connected to the plates 70, 71 of a rectifier 72 having a directly heated filament or cathode 73 connected to a secondary winding 74 on the transformer 69. @ne terminal of the directly heated filament or cathode 73 may be connected to the positive terminal 65. In general, there is no need for avoiding modulation of the high frequency source 45, and no high degree of filtering of the power supply 65 is required. A capacitor 75 connected between the output terminals 66 and 67 may be sufficient. However, if it should for some reason be desirable to improve the filtering of the supply 65, it will be readily appreciated by those skilled in the art that a better filtering arrangement could be used.

The transformer 69 may have a primary 76 connected to terminals 77 and 7S which are, in turn, connected to a suitable plug 79 to be inserted in a suitable outlet, which may supply 60 cycle single phase power, for example.

An important feature of the invention is in the provision of means for automatically regulating the spacing of the plates 17 and 18 relative to the oppositely facing surfaces of the plank 12, to control the high frequency current through the plank 12 and prevent excessive current which might otherwise cause breakdown of the fibrous structure of the wood. According to this feature, a relay St) may have a coil S1 connected in series with one of the power lines leading to tl e power supply 65, for example the line leading to the input terminal 77, and this relay St) may have a movable contact S2 engaged with one fixed Contact 83 when the current is below a predetermined value and engaged with a Contact 84 when the current is above a predetermined value, the contact 82 being intermediate the contacts 83 and 84 when the current is between such preterrnined values. The movable contact 82 may be connected to a terminal 85 arranged to be connected to a source of D.C. power, a terminal 86 being arranged to be connected to the other terminal of such source of power. The movable contact 3 may be connected to one side of an operating coil 87 of a relay 88 while the contact 84- may be connected to one terminal of an operating coil S9 of a relay 9G. The other terminals of the relay coils 87 and 89 may be connected to the terminal 86, so that when the movable contact 82 of the relay 80 engages the contact S3, the coil 87 will be energized, while when the movable contact 82 engages the contact 84, the operating coil 89 will be energized.

The relays 88 and 90 may have contacts arranged for energizing the motor 36, with the relay S8 being arranged to energize the motor to rotate in one direction and with the relay 90 being arranged to energize the motor to rotate in the opposite direction. In particular, the motor 36 may be a D C. motor having an armature 91 with one armature brush 92 connected to terminals 93 and 94 on the relays 88 and 90, respectively, and with another armature brush 95 connected to terminals 96 and 97 on the relays 83 and 90, respectively. The contacts 93 and 96 of the relay 83 are respectively arranged to be engaged by movable contacts 9S and 99 which are respectively connected to the terminals 86 and 85, while the contacts 94 and 97 of the relay 90 are respectively arranged to be engaged by movable contacts 100 and 101, respectively connected to the terminals 85 and 86. With this circuit, with the relay 88 energized, the armature 91 will rotate in one direction while with energization of the relay 90, the armature 91 will rotate in the reverse direction. It may be noted that the motor 36 may have a lield winding 102 connected between the terminals 85 and 86.

In operation of the machine illustrated in Figures 1 and 2, the plank 12 may be disposed onthe table 11 with the rollers 13-16 acting to align the plank 12 between the plates 17 and 18. The terminals 85 and 86 may be connected to a suitable source of D.C. power and the plug 79 may be inserted in a suitable outlet to energize the supply 65. This will energize the high frequency 'supply 45. The capacitors 60 and 62 may be adjusted to obtain the desired frequency of operation. In the event that the plates 17 and 18 are spaced too far from the oppositely facing surfaces of the plank 12, as may be ordinarily the case in the initial operation of the machine, the load on the supply 45 will be very low, and since the supply 45 is operated with either class B or class C bias, preferably class C bias, the power input to the device 45 will be relatively low. This will result in the low current to the power supply 65 and the contact 82 may be engaged with the contact 83 to energize the relay 88 and cause the armature 91 of the motor 36 to rotate in one direction. This direction may be such as to cause the plates 17 and 18 to move toward each other. When the plates 17 and 1S are closely adjacent to, or engaged with, the oppositely facing surfaces of the plank 12, the current through the plank 12 will be increased, to increase the loading on the high frequency supply 45, to increase the power drawn from the supply 65 and to increase the current through the relay coil 81. This current may be sufficient to draw the movable contact 82 out of contact with the fixed Contact 83, but insuicient to engage the movable contact 82 with the fixed contact 84, so that the armature 91 of the motor 36 will be deenergized. The spacing of the plates 17 and 18 will then It sometimes happens that after an initial current flow through the wood or like material being treated, the effective resistance of the material will be greatly reduced, to thus tend to increase the current flow therethrough. This increased current ow could cause breakdown of the cellular structure of the wood and damage thereto. The machine of Figures 1 and 2 automatically operates to prevent such excessive current and damage to the wood. In particular, if the current through the wood or other material under treatment should increase, the loading of the source 45 will be increased, to increase the loading on the power supply 65. This will increase the current through the relay coil 81 which may cause the movable contact 82 to engage the fixed contact 84 to energize the coil 89 of the relay 90. This will connect the brushes 92 and 95 of the armature 91 to the terminals 85'and 86 and the armature 91 will be caused to rotate in a direction such as to cause movement of the plates 17 and 18 away from each other. After the current has been reduced to a safe value, the current through the coil 81 may be reduced to allow the movable contact 82 to return to a position intermediate the contacts 83 and 8,4 with the motor armature 91 being then deenergized. Hence, this circuit operates to provide a maximum current through the material under test to obtain dehydration in the shortest time possible, but at the same time, the circuit prevents damage to the material under test which might otherwise arise from excessive currents.

Referring now to Figure 3, reference numeral 102 generally designates another preferred form of machine constructed according to this invention, the machine 102 being particularly arranged for the treatment of lignite, coal or similar materials. As diagrammatically illustrated in Figure 3, the machine 102 may comprise a conveyor belt 103 in a continuous loop about drive rollers 104 and 105 and arranged to receive material from a chute 106 `and deliver such material to a second chute 107. The material carried by the belt 103 is arranged to pass between a pair of electrodes 108 and 109, preferably in the form of plates having facing surfaces of relatively large area, and preferably with the plate 108 in spaced parallel relation above the top material-carrying surface of the belt 103 with the plate 109 located below the belt 103. The plates 108 and 109 may be connected to output terminals 111 and 112 of a source of high frequency voltage 113, which may preferably be in the form of an oscillator such as the oscillator 45 in the machine of Figures l and 2, as described in detail above. The oscillator may have power inlet terminals 114 and 115 connected to output terminals 116 and 117 of a power supply 118 iwhich may have input terminals 119 and 120 arranged for connection to a suitable source of electrical power, for example, a source of 60 cycle single phase alternating current. The power supply 118 may preferably be constructed like the power supply 65 as described above in detail in connection with the machine of Figures 1 and 2.

A s previously indicated, the tmachine 102 is particularly adapted for the treatment of coil and similar materials, especially lignite. Such materials, although they may be originally derived from vegeta-ble substances, are essentially mineral materials. In particular, coal is derived from vegetable sources by a process whereby the vegetable matter is converted to mineral matter, primar* ily by a separation of O and H2O from the C of cellulose (C6H1o05) m. In effect, the hydrophilic character of the OH-containing cellulose molecule is destroyed. In lignite, the wood structure is still apparent; but the material is actually converted already to mineral matter and the free C and other mineral matter therein have not yet lost completely the loosen orientation of cellulose even though the cellulose molecules per se are substantially destroyed.

With mineral materials, as pointed out heretofore, there is no continuous phase of water, except under unusual circumstances, and the material may have a relatively high impedance, so that there may be substantial spacing between the electrodes and the material and still obtain a high potential gradient within the material, and actual contact between the electrodes and the material is not necessary or even desirable. The plates 108 and 109 forming the electrodes may therefore be so disposed as to be out of contact with the material under test. The conveyor belt 103, of course, should be of an insulating material, although it is possible that the machine might be operated with the belt 103 of a conductive material.

The time interval required for dehydration of the material may be so short that the conveyor belt 103 may be operated continuously at the relatively high speed such as is ordinarlyemployed in conveying such materials. However, to insure proper drying, a rheostat 120a in series with a eld 120b of a D.C. motor 120e driving the conveyor 102 may be controlled by a controller 120d (which may be similar to the control system including relay and motor 36) in circuit with the input ofpower supply 118 to increase the conveyor speed when the oscillator load decreases and decrease the speed when the oscillator load increases.

It may be noted that the dehydration methods and apparatus of this invention are very efficient since the energy output of the high frequency sources are applied in the most efficient manner to the dehydration of the material, without unnecessarily generating unusable heat. The high frequency supply, such as the oscillator 45 may be comparatively efficient and may have an efficiency of over 75%, While thepower supply, such as the power supply 65 may have an eiliciency of over 90%. The load on the apparatus is automatically reduced as the dehydration takes place. Further, the apparatus is very compact and readily operated, and does not require any appreciable labor in operation.

Referring now to Figure 4, reference numeral 121 generally designates another preferred form of moistureremoving machine constructed in accordance with the principles of this invention. The machine 121 may be formed as an integral part of a paper-making machine in which rolls 122, 123 and 124 are the press rolls of a clover lea-rc press with paper 125 moving through the rolls 122-124 in a direction as indicated. A pair of rolls 126 and 127 may engage the paper 125 to feed it from the rolls 122-124. Intermediate the clover leaf press rolls 122-124 and the pinch rolls 126 and 127, moistureremoving means may be provided, in accordance with the principles of this invention. Such means may comprise a pair of electrodes 128 and 129 between which the paper 125 passes, the electrodes 128 and 129 being connected to output terminals 130 and 131 of a high frequency supply 132 which may preferably be in the form of an oscillator such as the oscillator 45 described in detail above in connection with Figures 1 and 2. The oscillator 132 may have input power terminals 133 and 134 connected to output terminals 135 and 136 0f a power supply 137 having inlet terminals 138 and 139 arranged to be connected to a suitable source of electricity, such as a source of 60 cycle single phase alternating current. The power supply 137 may preferably be constructed like the power supply 65 described above in connection with Figure 2.

As pointed out heretofore, it is highly desirable with vegetable fibrous materials such as paper that the electrodes be in eifective contact with the material to be treated. A specific feature of the machine 121 is in the construction of the electrodes 128 and 129, as illustrated in Figure 5. Referring thereto, the electrodes 12S and 129 may have portions 140 and 141 which extend inwardly in vertical alignment with opposite edge portions of the paper 125 and are preferably in overlying relation to such edge portions of the paper 125. The portions 140 and 141 may have ribs 142 and 143 providing rounded contact areas for smooth engagement with the paper, the ribs 142 and 143 preferably extending in a direction generally parallel to the direction of movement of the paper. To insure contact between the paper and the ribs 142 and 143, the lower surfaces of the ribs 142 and 143 may be located below a plane tangential to the undersurface of the roll 123, and tangential to the upper surface of the roll 127 (or lower surface of the roll 126).

ln the operation of the machine 121, the high frequency voltage applied to the electrodes 12h` and 129 by the source 132 will produce a current ow transversely through the paper. Initially, this current ow may be relatively large due to the conduction of current through the moisture in the paper but as the moisture is removed from the paper, the resistance will be increased, to decrease the current. By virtue of the engagement of the electrodes with the opposite edge portions of the paper, dehydration of the paper is insured. The moisture-removal may be accomplished very rapidly, so that the paper may be driven at a relatively high speed without necessitating extremely long lengths for the electrodes 128 and 129. As pointed out heretofore, it is highly desirable for eicient operation that the electrodes should be effectively in direct Contact with the paper, paper being a vegetable fibrous material having a relatively high conductivity with moisture therein.

It will, accordingly, be apparent that this invention provides methods and apparatus for moisture-removal which are very efcient and reliable in operation, achieve a degree of moisture-removal not possible with prior art methods and apparatus, and which are very compact, readily manufacturable, and easily operated.

Q (Isl It will be understood that modications and variations may be effected without departing from the spirit and scope of the novel concepts of the present invention.

We claim as our invention:

1. In a machine for treating material to remove moisture therefrom, a pair of electrodes arranged to receive the material therebetween, adjustment means mechanically coupled to at least one of said electrodes for adjusting the spacing therebetween, reversible electro-mechanical means coupled to said adjustment means, a source of high frequency voltage including a class-C output stage coupled to said electrodes, power supply means for applying voltage to said stage, a relay responsive to current drawn by said stage from said power supply means and including Contact means operated in one direction when said current is less than a certain value and operated in the reverse direction when said current is greater than a certain value, means controlled by operation of said contact means in said one direction for energizing said electro-mechanical means in a direction to decrease the spacing between said electrodes, and means controlled by operation of said contact means in said reverse direction for energizing said electro-mechanical means in a direction to increase the spacing between said electrodes, whereby the high frequency power applied to the material is maintained substantially constant within limits.

2. In a machine for treating material to remove moisture therefrom, guide means for receiving and positioning the material in a certain region, a pair of electrodes on opposite sides of said region, a pair of racks connected to and disposed in transverse relation to said electrodes and disposed in spaced parallel relation to each other, a gear positioned between and having opposite sides meshed with said racks to control movement of said electrodes conjointly toward or away from said region, reversible electro-mechanical means coupled to said gear, a source of high frequency voltage including a class-C operated output stage coupled to said electrodes, power supply means for applying voltage to said stage, a relay responsive to current drawn by said stage from said power supply means and including Contact means operated in One direction when said current is less than a certain value and operated in the reverse direction when said current is greater than a certain value, means controlled by operation of said contact means in said one direction for energizing said electro-mechanical means in a direction to decrease the spacing between said electrodes, and means controlled by operation of said contact means in said reverse direction for energizing said electro-mechanical means in a direction to increase the spacing between said electrodes, whereby the high frequency power applied to the material is maintained substantially constant Within limits.

References Cited in the le of this patent UNITED STATES PATENTS 1,307,341 Brinton June 24, 1919 1,626,766 Tompkins May 3, 1927 2,042,145 Darrah May 26, 1936 2,147,689 Chaffee Feb. 21, 1939 2,23l,457 Stephen Feb. ll, 1941 2,458,563 Collins Ian. ll, 1949 2,504,969 Ellsworth Apr. 25, 1950 2,505,025 Zottu Apr. 25, 1950 2,506,814 Sayre May 9, 1950 OTHER REFERENCES Terman: Radio Engineers Handbook 1943 edition, published by McGraw-Hill, pp. 480-484. 

